Limits on the number of spacetime dimensions from GW170817
Abstract
The observation of GW170817 in both gravitational and electromagnetic waves provides a number of unique tests of general relativity. One question we can answer with this event is: do largewavelength gravitational waves and shortfrequency photons experience the same number of spacetime dimensions? In models that include additional noncompact spacetime dimensions, as the gravitational waves propagate, they "leak" into the extra dimensions, leading to a reduction in the amplitude of the observed gravitational waves, and a commensurate systematic error in the inferred distance to the gravitational wave source. Electromagnetic waves would remain unaffected. We compare the inferred distance to GW170817 from the observation of gravitational waves, d_{L}^{GW}, with the inferred distance to the electromagnetic counterpart NGC 4993, d_{L}^{EM}. We constrain d_{L}^{GW} = (d_{L}^{EM}/Mpc)^{γ} with γ = 1.01^{+0.04}_{0.05} (for the SHoES value of H_{0}) or γ = 0.99^{+0.03}_{0.05} (for the Planck value of H_{0}), where all values are MAP and minimal 68% credible intervals. These constraints imply that gravitational waves propagate in D=3+1 spacetime dimensions, as expected in general relativity. In particular, we find that D = 4.02^{+0.07}_{0.10} (SHoES) and D = 3.98^{+0.07}_{0.09} (Planck). Furthermore, we place limits on the screening scale for theories with D>4 spacetime dimensions, finding that the screening scale must be greater than ~ 20 Mpc. We also place a lower limit on the lifetime of the graviton of t > 4.50 × 10^{8} yr.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 July 2018
 DOI:
 10.1088/14757516/2018/07/048
 arXiv:
 arXiv:1801.08160
 Bibcode:
 2018JCAP...07..048P
 Keywords:

 General Relativity and Quantum Cosmology;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 v3: fixed typo in abstract